The U.S. Transportation Security Administration will let people carry small pocketknives onto passenger planes for the first time since the Sept. 11 terrorist attacks, along with golf clubs, hockey sticks and plastic Wiffle Ball-style bats.

The agency will permit knives with retractable blades shorter than 6 centimeters (2.36 inches) and narrower than 1/2 inch, TSA Administrator John Pistole said today at an aviation security conference in Brooklyn. The change, to conform with international rules, takes effect April 25.

Passengers will also be allowed to board flights with some other items that are currently prohibited, including sticks used to play lacrosse, billiards and hockey, ski poles and as many as two golf clubs, Pistole said.

“This policy was designed to make the lives of TSA staff easier, but not make flights safer,” Stacy Martin, president of the Transportation Workers Union local that represents Southwest Airlines Co. flight attendants, said in a statement.

“While we agree that a passenger wielding a small knife or swinging a golf club or hockey stick poses less of a threat to the pilot locked in the cockpit, these are real threats to passengers and flight attendants in the passenger cabin,” Martin said.